The immune system is finely tuned to detect and eradicate foreign molecules and, at the same time, avoid over reactivity, which could result in destruction of normal tissues resulting in autoimmune or chronic inflammatory diseases. The initiation of a specific immune response is a well-orchestrated chain of events culminating in the activation of effector functions, such as the release of cytokines, production of specific antibodies and/or cellular cytotoxic activity.
The role of the immune system in human cancer has been under debate for several years. It has been puzzling, for example, that an increased incidence of malignant tumors is not observed in immunocompromised animals, such as nude mice. These animals are not as profoundly immunocompromised as one would expect, since they are able to mount significant anti-tumor immune reactivity. When severely immunocompromised transgenic mice of the Stat 1 −/−, IFNγR −/−, or RAG2 −/− genotypes were studied, the tumor incidence and the immunogenicity of cancers growing in these animals strongly supported the existence of an immune mediated anti-cancer reactivity with the capacity to control cancer development. Based on these results, the immunoediting model was developed (Dunn and Schreiber, Immunity, 21:137-148 (2004)).
Similarly, the modest increase in cancer incidence in therapeutically immunosuppressed, allo-organ transplanted patients seems to be explained by the early appearance of immunosuppression in epithelial cancers (Schüle J, et al., Breast Cancer Res Treat. 2002; 74:33-40; Wolfram R M, et al., Int J Cancer. 2000; 88:239-44, Petersen R P, et al., Cancer. 2006; 107:2866-72). The occurrence of spontaneous immune-mediated tumor regression, the correlation between tumor-infiltrating lymphocytes and prognosis, the occurrence of tumor specific cytotoxic T-lymphocytes and antibodies and the efficacy of immunostimulatory treatment all support a significant role of the immune system in the control or regulation of cancer progression.
These observations are also consistent with the results of Clinchy et al. (Clinchy B, et al., Cancer. 2007; 109:1742-9), showing that dysregulation of the immune system in cancer, with an enhanced capacity to produce IL-6, correlate to poor prognosis in radically resected colorectal cancer patients. Not even in the group of high risk patients with locally advance tumors, T3N1-2, did patients die from their cancer if their immune cells exhibited a normal production of IL-6. Similarly, Galon et al. (Galon J, et al., Science. 2006; 313:1960-4, Mlecnik B, et al., J Clin Oncol. 2011, 29:610-8) have shown that T-cell immune parameters strongly correlate to the prognosis in these patients.
The majority of human cancers of different origin induce immune mediated anti-tumor reactivity, but immunosuppressor mechanisms often appearing at an early stage, compromise the immune system. The existence of regional immunosuppression in the absence of systemic suppression (concomitant immunity), indicates a regional, systemic gradient of immunosuppression (Gorelik E., et al., Adv Cancer Res. 1983; 39:71-120). For instance, the function of immune cells can be more impaired near the tumor than in peripheral blood (Vose B M, et al., Int J Cancer 1977 20:895-902). Several factors may mediate this suppression (Ménétrier-Caux C, et al., Br J Cancer 1999 79: 119-130, Heimdal J H, et al., Scand J Immunol 2000 51: 271-278, Heimdal J H, et al., Scand J Immunol 2001 53: 162-170), but no fundamental mechanism has been identified (Kim R, et al., Cancer Res. 2006 Jun. 1; 66(11):5527-36, Mocellin S, et al., J Immunother 2001 24:392-407). The impact of the hostile intra-tumoral milieu has been described by several groups (Perdrizet G A, et al., J Exp Med. 1990; 171:1205-20, Yu P, et al., J Exp Med. 2005 201:779-91.) Immune reactivity against cancer can be suppressed at various levels, e.g., initiation, recruitment of effector cells to the tumor and migration of these cells within the tumor and their cytotoxic activity. Effector mechanisms present at the tumor site can also provide immune mediated cancer control.
Although data indicate that the immune system is of major importance for cancer control (Dunn G P, et al., Immunity. 2004 21:137-48, Galon J, et al., Science. 2006 313:1960-4, Koebel C M, et al., Nature. 2007 450:903-7, Clinchy B, et al., Cancer. 2007 109:1742-9, Teng M W, et al., J Leukoc Biol. 2008 84:988-93) malignant tumors continue to grow and the efficacy of immunotherapy is rather poor with an objective remission rate of 10-20%. There can be several reasons for this apparent paradox, e.g., tumors avoid recognition by the immune system due to tumor antigens being weak self-antigens, poor antigen presentation due to down-regulation of TAP and MHC I and II) or induction of tolerance or cancer related immunosuppression. The impact of an hostile intra-tumoral milieu is demonstrated by results from animal experiments (Perdrizet G A, et al., J Exp Med. 1990; 171:1205-20, Yu P, et al., J Exp Med. 2005 201:779-91.) and human tumors (Gajewski T F, et al., J Immunother. 2006 29:233-40, Whiteside T L, Oncogene. 2008 27:5904-12).
Different types of immunosuppressor cells, regulatory T-cells, immature dendritic cells (iDC), tumor associated macrophages (TAM) and myeloid derived suppressor cells (MDSC), can function substantially in cancer related immunosuppression. The immune balance is generally skewed to a Th2 dominance characterized by cytokines, such as IL-4, IL-10 and PGE2. Additionally, other immunosuppressor mechanisms, such as serum blocking factors, circulating immune complexes, enhanced IL-1Ra production and enhanced intra-tumoral proteolytic activity can function in cancer related immunosuppression.
While investigating mechanisms for induction of interleukin-6 (IL-6) in cancer patients, immunoregulatory peptide sequences derived from serum albumin were found (see e.g., U.S. Pat. Nos. 7,960,126; 8,110,347; and 8,110,347; as well as, US Publication No. 2010/0323370, each of which is hereby expressly incorporated by reference in their entireties. Interleukin-2 (IL-2) plays a major role in initiation and activation of the immune response and its capacity to induce lymphokine activated killer cells (LAK-cells), T-cell proliferation and cytotoxicity. Several reports have shown that peripheral blood mononuclear cells (PBMC) from cancer patients have a diminished capacity to both synthesize (Wanebo H J, et al., Cancer. 1986 57:656-62, Mantovani, G., et al., Diagn. Clin. Immunol. 1987 5: 104-111, Lauerova L, et al., Neoplasma 1999 46: 141-149) and respond to IL-2 (Tsubono M, et al., J Clin Lab Immunol 1990 33:107-115, Pellegrini P, et al., Cancer Immunol Immunother 1996 42:1-8). Soluble products from tumor explants or serum from cancer patients can inhibit cytokine production, inhibit IL-2 receptor expression (Botti C, et al., Intl J Biol Markers 1998 13:51-69, Lauerova L, et al., Neoplasma 1999 46:141-149) and/or reduce the proliferative capacity in normal T lymphocytes (Botti C, et al., Intl J Biol Markers 1998 13:51-69).
Integrins are a superfamily of transmembrane glycoproteins, found predominantly on leukocytes that mediate cell-cell and cell substratum interactions. Integrins play an important role in immune regulation, as well, in particular αLβ2, (Leukocyte Function Associated molecule-1, LFA-1) is of pivotal importance for the initiation and regulation of an immune response, tissue recruitment and migration of inflammatory cells and cytotoxic activity of lymphocytes (Hogg N, et al., J Cell Sci. 2003 116:4695-705, Giblin Pa., et al., Curr Pharm Des. 2006 12:2771-95, Evans R, et al., Cell Sci. 2009 122:215-25). In addition, LFA-1 is involved in the proliferative response to interleukin-2 (Vyth-Dreese F A, Eur J Immunol. 1993 12:3292-9) and some fragments of albumin bind to LFA-1 and/or the IL-2 receptor thereby modulating the functional properties mediated through these receptors including immune cell proliferation (see U.S. Publication No. 2011/0262470, which is hereby expressly incorporated by reference in its entirety). Despite these advancements, the need for more compositions to modulate the immune system, especially in individuals that have a compromised immune system and/or cancer, is manifest.